Tofu making is a labor intensive process and is prone to microbial contamination at various stages. There is significant variation of quality of product dependent on the human factors.
Batch curding of hot soymilk is done by adding a coagulant followed by gentle mixing, waiting, again gentle mixing and further waiting until the curd forms and separates from whey. The curd is then gently drained off whey and ladled into filter fabric lined forming boxes and the curd pressed by the application of mechanical force until it acquires the desired firmness. It is then cut into blocks which are then sold in bulk or package in water filled plastic tubs or vacuum packed. Each step is either performed manually or semi-automatically and has significant exposure to bacteria and requires human input.
In U.S. Pat. No. 5,094,975 Mar. 10, 1992 Chen, a continuous method of tofu production is described. The method comprises steps of simultaneously feeding substantially constant proportion of soymilk and an aqueous coagulant solution into a coagulator vessel; coagulating the soymilk and aqueous coagulant solution at an elevated temperature to obtain a gelatinous mixture comprising soybean curd lumps and whey; prior to substantial cooling of the gelatinous mixture after coagulation, separating at least a portion of the whey from the gelatinous mixture. The equipment described in the patent uses a coagulating vessel in which coagulation takes place and gelatinous products are transported to a washer. The coagulating vessel is not a length of holding tube in which materials travel at a constant rate while coagulation process is taking place.
A prior art method also exists for continuous curding of milk and whey milk for making ricotta cheese as described in "Production and yield of whole-milk Ricotta manufactured by a continuous process. 1. Materials and methods" by H. W. Modler and D. B. Emmons, Milchwissenschaft, Vol. 44 (11), pp 673-676, 1989.
However, it does not provide for the remaining steps in the process of making tofu and also does not give the operating parameters for curding soymilk. The Reynolds number based process description of the prior art is inadequate for the scaling of the process to industrial size operations even for ricotta cheese production.
The present invention addresses these problems and enables the continuous production of gelatinous soybean products such as tofu.